(1) FieId of the Invention
The present invention relates to a hose coupling, and in particular to a hose coupling suitable for use with spiral wire reinforced hoses.
(2) Description of the Prior Art
A typical hose coupling in the prior art consists in the main of a nipple with a corrugated or barbed surface on its external circumference for gripping the inside of the hose end firmly, an axially movable back nut for clamping the hose end in place about the nipple, and a main body having in its circumference an external thread for engagement with the back nut through its internal thread portion. The main body has at its opposite end either an external or an internal thread portion for connection with another length of hose with a coupling having a mated thread end.
In such a conventional hose coupler the nipple takes firm grip on the inside of the hose end through its wrinkled circumference, providing a tight leakproof seal at the point of connection, and the back nut clamps the hose securely, preventing accidental disconnection or looseness during fluid transfer service.
Those prior art hose couplers have been widely accepted and efficiently used with general purpose and other hoses made of rubber or synthetic resin material with smooth or plain inside and outside surfaces.
In the recent years, however, general demands for enhanced performance such as greater flexibility and resistance to pressures and temperatures have brought about a popular use of spiral wire-reinforced hoses. The hose of this type reinforces its body structure with a flight or fliqhts of helical wire of metal or synthetic resin wound along the entire hose length, either externally about the covering or internally imbedded between the outer and inner pliers.
These reinforced hoses, owing to the very presence of the spiral wire reinforcement, are normally more or less knotty or wrinkled in either or, in some products, both of their outside and inside surfaces, along the length. As a result, the prior art hose couplers have been found to suffer several hitherto unknown difficulties when used on such a reinforced hose.
First, with a spiral wire-reinforced hose having its inside surface wrinkled, the nipple inserted into the hose end leaves air gaps between their contacted corrugated surfaces, through which the transferred fluid can readily leak. In addition, the corrugation both in their mated surfaces does not insure a firm grip between the hose and the nipple.
Secondly, when the hose is corrugated in the outside, some difficulty will be encountered, after inserting the nipple into the plain inside of the hose, in moving the back nut over the knotty hose outside for fit engagement with the nipple. An improper enqagement between the back nut and nipple can result in the hose easily coming off from the coupling.
In the case of a reinforced hose having both sides wrinkled, the aforesaid problems are doubled. Further, since it is somewhat difficult and awkward to bring the back nut over the corrugated outer surface of the hose in engagement with the nipple, the gripped hose end can most likely to stand clamped in a distorted state where the pressures exerted by the back nut on the hose outside cause the hose inside to contact with the nipple circumference in points at which the ridges of their surface corrugations. Consequently, the fluid can easily leak in drips or, in an extreme case, in spurts through openings defined between these contacted points in the mated surfaces.
With the above-mentioned problems in the background, great demand has been placed on the development of an improved hose coupling capable of efficient service on spiral wire-reinforced hoses with corrugated surfaces, without causing a leak or accidental disconnection during use.
It is therefore a main object of the present invention to provide an improved hose coupler particularly suitable for spiral wire-reinforced hoses having their inside and outside surfaces embossed by the helical reinforcement provided either wound about the covering or internally imbedded, which is capable of tight leakproof seal and firm grip, without causing an air gap in the engaged surfaces of the nipple wrinkled circumference and the hose knaggy outside.
The above and other objects, features and advantages of the present invention are accomplished by the structure of the hose coupling that, according to one preferred embodiment, features a tubular seal fixedly secured about the nipple circumference and formed to have its axial length to measure not less than the pitch of the reinforced wire helix in the hose. The hose coupling also includes a cylindrical sleeve adapted to enclose the engaged hose end and about the a nipple and having at its forward end an inwardly-extending projection formed in the inside thereof for gripping on the hose outside. The sleeve has at least a longitudinal slit cut in the wall thereof so that the sleeve can be both radially outwardly spread and inwardly compressed to permit insertion and engagement of the hose end therein.
The relative position of the projection in the sleeve to the seal in the nipple is designed that, when the engaged hose end about the nipple is encased in place within the sleeve, the projection engages the hose outside just over the seal. As a consequence, the hose is sealed to all way around the circumference on both of the corrugated inside and outside surfaces, insuring a tight leakproof seal.
The invention will be better understood by reference to the accompanying drawings, taken in conjunction with the following discussion.